But now, for the first time, a staggering fiscal cost has been calculated: $520 million annually. A new study, described as the most comprehensive look ever at the expense of homelessness on a community, has determined that more than $3 billion was spent over a six-year period in the county on services such as trips to the emergency rooms, jail stays and mental health care. “Home Not Found: The Cost of Homelessness in Silicon Valley” also identified how a small group of about 2,800 persistently homeless alone cost the county about $83,000 each, per year. “What this shows is that having people live out in the open is tragic for the individual, destabilizing for the community and, at the end of the day, very expensive for the public,” said Dan Flaming, president of Los Angeles-based Economic Roundtable, which produced the report for Santa Clara County and the nonprofit Destination: Home…. The study… tracked more than 104,000 homeless in the county from 2007 to 2012, mining data from sources that included hospital and criminal-justice records…. The county has 7,567 homeless — the nation’s seventh-highest total — according to the most recent published survey, the 2014 Annual Homeless Report to Congress.